Revision notes on res ipsa loquitur - a new requirement of the revised A level specifications.
Following the Examiners Report on AQA Unit 2 it appears that many students dropped marks on Question 2 by failing to demonstrate a secure understanding of res ipsa loquitur (RIL)
Based upon my own experience, students tend to fall into the following traps:
1) Merely listing that RIL means the thing speaks for itself - without any indication of context or the effect (what are the legal implications of RIL?)
2) Failure to state the 3 conditions required for the claimant to assert RIL.
3) Using RIL within an answer where causation is known.
Summary Revision Notes:
RIL allows a court to establish breach of duty (prima facie negligence) without necessarily having tested the evidence by way of examination of expert reports.
The key case of Scott v. London & St Katherine Docks Co  3 H&C 596 (concerning the falling sugar sack) establishes that three conditions are required for the claimant to be able to rely upon RIL:
a) The object which caused the damage was under the control of the defendant or a person for whose negligence the defendant will liable (consider vicarious liability);
b) Causation is unknown; and
c) Without negligence the accident would not normally occur.
In a) above, students may wish to use the railway door case of Easson v. LNER  2 KB 421 (CA) to contextually illustrate the point on control.
Whether b) is relevant in the examination, will be dependent upon the wording and content of the problem question. Higher level answers will point out that if causation is unknown RIL does not apply and the court will decide upon the facts whether negligence has been established.
For c) students could highlight a number of cases, but a selection fromScott v. St. Katherine Docks; Ward v. Tesco and Cassidy v. Ministry of Health (primarily a medical negligence case) would illustrate this point neatly.
Effect of Res Ipsa Loquitur
In the event the 3 conditions above are fulfilled, RIL raises a prima facie presumption of negligence against the defendant. However, if the defendant can explain how the accident could have happened without negligence, the defendant has rebutted the prima facie presumption and the claimant must try to prove the defendants negligence according to the normal rules of duty breach, causation and remoteness. However, whilst RIL creates a rebuttable presumption, it does NOT reverse the legal burden of proof - the Privy Council held that this remains on the claimant throughout (Ng Chun Pui v. Lee Cheun Tat  RTR 298 (PC)) - better students will be able to apply the effect of RIL and state the consequences for the parties concerned in the problem question.
Whilst students need not make be a long laboured points on this, a short extra paragraph, outlining aspects of the above where appropriate should add to the quality and depth of student response.